Grounding concepts of contemporary electrical and diesel-electrical rail vehicles or railway vehicles must equally meet both the requirements which are made in terms of fault-free operational current feedback into the rail—that is to say the operational grounding—and the requirements made in terms of effective protection against electrical shocks, that is to say the protective grounding.
The protection against electrical shocks requires all the metallic parts of the wagon body which could be connected to a voltage in the case of a fault to be connected with as low an impedance as possible to the railway ground, i.e. for example to the rails. Such a fault situation could take the form, for example, of a contact wire tearing off an overhead line of the route and entering into contact with the wagon body. In such a case, the wagon body would in fact be connected to a high voltage if no efficient protective grounding were provided.
Protective grounding is implemented in previously known rail vehicles using, for example, ground cables which are connected to the wheel set contacts of the rail vehicle.